Fireside Deposits, Sootblowers and Offline Cleaning

Keep gas-side surfaces effective

Fireside cleaning removes combustion deposits from surfaces exposed to flame and flue gas. Soot, fly ash and slag can insulate heating surfaces, obstruct gas passages, alter draft and create corrosion or fire hazards. Waterside scale is a different problem on the fluid side of the metal. A clean fireside does not prove the waterside is clean, and additional water treatment cannot remove a gas-side deposit already attached to a tube bank.

A soot layer adds thermal resistance. At comparable load, water condition and air conditions, declining heat absorption may appear as rising stack temperature and greater fuel demand. Deposits can also increase gas-path pressure loss and change fan/draft behaviour. These observations are clues rather than a unique diagnosis: changed load, excess air, air infiltration and instrument error can produce similar trends. Compare readings on a compatible basis before deciding that cleaning is needed.

Online sootblowing equipment

A sootblower directs a designed cleaning jet across selected surfaces. Depending on the installation it can use steam, compressed air or another approved medium. Rotary or retractable lances position nozzles to sweep their intended paths. Retractable designs limit the time vulnerable parts remain exposed to high gas temperature. The valves, drive, drains and position indication form a system; a turning motor alone does not prove the lance is moving correctly.

Steam supplies must have the required condition before blowing. Wet steam or trapped condensate can subject tubes and lance components to thermal or mechanical damage. Drain and warmup arrangements must follow the maker’s sequence and safe discharge route. Compressed-air systems have their own pressure, moisture and capacity limits. Do not increase pressure to make a weak cleaning result disappear without evaluating the specified equipment limits and cause.

Sootblower operation must be coordinated with boiler load, draft and emissions conditions. Blowing dislodges material into the gas stream, so collectors, hoppers and discharge systems must be ready. The control program may sequence lances to manage furnace conditions and avoid unnecessary simultaneous demand. Verify the intended start position, movement, shutoff and return/retraction state using the approved indications. A stuck lance or leaking medium valve requires the defined response rather than repeated blind restarting.

Avoid damage and overcleaning

Cleaning jets can erode tube metal if alignment, pressure, travel or frequency is wrong. A nozzle aimed repeatedly at one spot is different from a properly sweeping jet. Worn nozzles, incorrect replacement parts and failed drives can change the exposure. More frequent blowing can consume steam/air, increase wear and disturb operation without improving the real underlying problem.

Use the plant’s condition-based or scheduled program and trend the response. Compare before/after gas temperature and pressure loss at similar operating conditions. A lack of expected improvement can mean the deposit is unsuitable for online removal, a blower fault exists, another problem controls performance, or measurements are not comparable. Do not diagnose success from noise or a visible stack cloud alone.

Offline access, cleaning and inspection

Offline cleaning requires the approved shutdown, cooling, isolation and verification before opening access points. Account for fuel, electrical power, hot gas, stored pressure, connected equipment and possible confined-space hazards. Dust may contain harmful constituents; material identification, exposure controls, suitable extraction and waste handling are part of the job. Ordinary compressed-air blowing can spread dust or create combustible clouds and is not a generic safe cleaning method.

Mechanical brushing, vacuum collection or other methods must suit the tube material and deposit. Chemical or water washing is used only where the manufacturer and approved plan permit it, with control of corrosion, moisture retention and contaminated effluent. Do not direct cold water onto hot surfaces or improvise an acid wash from a study example. Refractory, seals, insulation, tubesheets and supports need inspection as well as visible soot removal.

Deposits can conceal cracks, erosion, corrosion or overheating. Record findings and arrange the required competent inspection rather than immediately closing up a newly clean surface. Replacement gaskets, access-door closure, guards, instruments and the gas path must be restored under the return-to-service procedure. A tool or blocked passage left inside the unit can create a new hazard.

Link cleaning to combustion and maintenance

Investigate why deposits formed. Poor atomization, inappropriate air distribution, fuel characteristics, burner condition and operating duty can contribute. Cleaning without correcting a recurring cause may restore heat transfer briefly while the unsafe or inefficient condition returns. Record cleaning method, inspected condition, removed waste, defects, restoration and performance observations. The next shift should know whether the boiler is ready, under restriction or awaiting inspection, rather than simply being told that it is clean.

Comparison aid

Source notes

Official scope and technical references checked 2026-10-17: Reference 1; Reference 2; Reference 3.